Salt Quench Hardening: An Overview

This presentation will provide the general audience with an overview of salt quench hardening, the pros and cons of working with salt, the benefits of salt quenching, and some of the various processes as well as types of equipment used when working with salt quench applications. We will answer the question “why salt?” by comparing it to traditional oil quench applications, by considering the characteristics of salt and how it promotes hardenability, ductility, tensile and yield strength, and by looking at the benefits of salt for distortion control, heat extraction, ease of washing, and the “green” side of recycling. We will address equipment layout configurations and the ancillary pieces of equipment required for an efficient operation, based on production requirements with a consideration of the specific part weight, geometry and annual volume. We will touch on NFPA guidelines and general safety practices. Finally, we will look at various processes associated with quenching in salt – austempering and marquenching, and as we conclude the presentation, we will discuss how material and process changes can lead to engineering optimization opportunities for “light-weighting”, mechanical feature enhancements, and process reduction.

Evaluation of the characteristics of an AISI 1045 steel quenched in different concentration of polymer solutions of polyvinylpyrrolidone

Quench hardening aims at the microstructural transformation of steels in order to improve hardness and mechanical strength. The aim phase is, in most cases, the martensite. It is necessary to heat the material until it obtains its austenitization and quenching by immersion in a fluid. Currently, it is common to use watery polymeric solutions in this procedure. These fluids, which are the mixture of polymers in water, vary their thermal exchange capacity depending on the concentrations applied. The increase in concentration minimizes the removal of heat from the part, reducing the formation capacity of martensite, and developing a lower hardness and strong steel. In this work, microstructural characteristics and properties of AISI 1045 steel quenched in solutions based on polyvinylpyrrolidone (PVP) in 10, 15, 20, and 25% concentration were evaluated. The microstructural characterization quantified the percentage of the phases in each concentration, demonstrating a reduction of martensite as the concentrations were high. The investigation of the samples by x-ray diffraction confirmed the absence of austenite retained in the material. Furthermore, a microhardness scale between the core and the surface was constructed, in which a reduction gradient of the indices of this property towards the core of the sample was evidenced.

Nanoindentation-Based Micro-Mechanical and Electrochemical Properties of Quench-Hardened, Tempered Low-Carbon Steel

The nanoindentation technique is widely used to measure the micro-scale mechanical properties of various materials. Herein, the nanoindentation-based micro-mechanical and electrochemical properties of low-carbon steel were investigated after quench hardening and tempering processes. The steel was produced on a laboratory scale and subjected to quench hardening separately in two different media-water and brine (10 wt% NaCl)-and subsequent moderate temperature tempering. Microstructure analysis revealed that the lath martensite phase formed after all heat treatments, having different carbon percentages ranging from 0.26% to 0.58%. A ferrite phase was also observed in the microstructure in three different morphologies, i.e., allotriomorphic ferrite, idiomorphic ferrite, and Widmanstätten ferrite. Nanoindentation analysis showed that the brine quench hardening process provided a maximum twofold improvement in indentation hardness and a 51% improvement in stiffness with a 30% reduction in reduced elastic modulus compared with as-received steel. Electrochemical performance was also evaluated in a 1% HNO3 solution. The water quench-hardened and tempered sample exhibited the highest corrosion resistance, whereas the brine quench-hardened sample exhibited the lowest corrosion resistance among all heat-treated samples.

DEUTSCHE EDELSTAHLWERKE CRYODUR 2067

Deutsche Edelstahlwerke Cryodur 2067 is a high-carbon, 1.5% chromium, alloy cold-work tool steel. In view of its higher hardenability than that of the non-alloy, water-hardening, cold work tool steels, this steel can be oil quenched, a factor that minimizes dimensional changes during quench hardening. Cryodur 2067 is suitable for short run tooling in applications requiring high surface hardness. This datasheet provides information on composition, physical properties, hardness, and elasticity. It also includes information on forming, heat treating, and machining. Filing Code: TS-786. Producer or source: Deutsche Edelstahlwerke Specialty Steel.

Causes of Distortion during High Pressure Gas Quenching Process of Steel Parts

Quench hardening is a necessary process for improving the mechanical and fatigue performance of load bearing steel components, but liquid quenching can lead to large distortions. High pressure gas quenching is becoming a more popular choice, with the assumption that a slower cooling rate will lead to less distortion. While true for certain geometries, nonlinearities in distortion response can make understanding the dimensional change of a component difficult due to the inherently complex behavior during quenching. Through the use of modeling, and a specially designed coupon, the out-of-round distortion of an eccentric bore is examined for common high-pressure gas quenching conditions. The causes of distortion are examined and explained using the model, with insights into why the cooling rate has a nonlinear relation with distortion.

Distortion Minimization of Bevel Gear Press Quench Hardening Process Using Computer Modeling

Press quenching is used to harden gears with large sizes or thin-wall sections while keeping distortion under control. For carburized gears, controlling distortion is critical because only a limited amount of the carburized case can be machined off after hardening. In comparison to immersion oil quenching, the press quench process involves more process parameters due to the thermal and mechanical effects from the tooling on the parts. The press quench tooling and process designs are mainly experience based, with iterative trials needed before obtaining an acceptable process. Computer modeling provides a means for understanding the effects of tooling and process parameters on distortion, which can be used to optimize the process and tooling design. One paper using modeling to simulate the gear responses during a press quench process was published in the 23rd IFHTSE Congress, Savannah, Georgia, USA, 2016.[1] The bevel gear was made of carburized AISI 9310, and the radial shrinkage and taper of the inner diameter were the main distortion modes. The modeling results showed that the expanders were not effective in controlling the distortion of the inner diameter of this gear. Based on the simulation results, an oversized plug was proposed to replace the expanders to effectively control the inner diameter of the gear. However, the taper distortion of the bore was not corrected effectively. In this follow-up paper, the effect of a customized plug configuration is modeled, and an optimized plug configuration is designed to further reduce the distortion of the bore from the quench hardening process.

Pengaruh Kecepatan Rotasi Pahat dan Kecepatan Pengelasan terhadap Sifat Mekanis Hasil Pengelasan Friction Stir Logam Tak Sejenis Aluminium 5052 H3 dan Tembaga

Tujuan penelitian ini meneliti pengaruh variasi kecepatan rotasi pahat dan kecepatan pengelasan, terhadap sifat mekanis pengelasan FSW AA 5052 H3 dengan tembaga. Pengelasan FSW dilakukan dengan menggunakan mesin milling CNC. Tool shoulder dibuat dengan baja H13 yang dikeraskan dengan metode quench hardening dengan pin berbentuk kerucut. Pengelasan FSW dilakukan dengan variasi rotasi pahat: 2850 rpm, 3000 rpm, dan 3150 rpm, Kecepatan pengelasan FSW: 100 mm/min dan 120 mm/min. Hasil penelitian menunjukkan bahwa kekuatan tarik tertinggi dihasilkan pada pengelasan dengan kecepatan putaran 3000 rpm dan dengan kecepatan pengelasan 100 mm/menit yaitu sebesar 223 MPa.

WEAR RESISTANCE OF STRUCTURAL STEELS AS A RESULT OF BORONISING OPERATIONS

This paper presents the results of investigations on the effect of thermochemical treatment, boronising and chemical composition of selected structural steels on their wear in sliding friction process. The operation of boronising on C45, 37CrNiMo, 42CrMo6, 41Cr4, 50CrSi4-4 steels was performed by powder method at 950°C for 8 h. Following this operation, rod sections of the test steels were subjected to quench hardening from 850°C with isothermal holding at 300°C for 1h. The assessment of the construction, thickness and microhardness of boronised layers depending on the level of carbon and alloying elements in chemical composition of analysed steels was made. The testing for wear resistance of steels after boronising was carried out with the sliding friction method by applying a load of 150 N, counter-sample rotational speed of 1000 rpm and using aqueous solution of potassium chromate as a cooling medium. The metallographic observations of the structure and thickness measurement of the boronised layers were carried out using a light microscope, while the identification of phases was made by the X-ray qualitative analysis method. The hardness and microhardness measurements were taken by the Vickers method.